 Francis Bacon  Karl Popper  Thomas Kuhn

The Logic of Scientific Discovery Hypothesis testing Asymmetry Negative evidence Positive evidence Logical asymmetry The only relevant evidence is negative evidence Scientists should refute their hypothesis

 Popper was very fond of a picture of scientific evolution modelled on natural selection. That analogy may be genuinely helpful in some respects, but the idea that hypothesis generation is like random mutation is potentially misleading.  Hypothesis generation is highly constrained and directed, and would have to be if science is possible at all.

 Popper’s second idea of testing as falsification has also been criticised in the context of pure science, and this too may face special additional difficulties in the context of engineering.  Popper has been criticised for making it sound as though hypotheses are much easier to refute than they really are. Nevertheless, his logical point is sound.

 Kuhn’s big idea is also a contrast, but it is the contrast between rules for research and what he called exemplars, the core meaning of his notorious and protean term ‘paradigm’.  How do exemplars differ from rules? Kuhn was struck by a feature of research during periods of what he came to call ‘normal science’.  Members of the research community in a particular speciality act as if they shared the same rules of research.

tend to agree on which are the important problems tend to agree on how those problems should be tackled tend to agree on the appropriate standards for judging whether a particular solution is sound

 Exemplars are neither rules nor general principles. Rather, they are specific, canonical problem solutions in a particular scientific specialty.  They are particular solutions, but they nevertheless function as general models because, according to Kuhn, they set up similarity relations, so that the scientists can work by imitation and analogy rather than by rules.

 Because of the similarity relations that the exemplars elicit, certain unsolved problems come to look similar to the problems that the exemplars solve.  Those are the problems the scientist will pick, the outstanding problems that look like problems that have already been solved, and so the problems for which there seems every possibility of successful solutions.

 Scientists will naturally try to apply techniques similar to those that worked so well in the exemplars.  That is only rational: since the problems were selected because of their perceived similarity to problems the scientists have already solved, they will try similar solutions to see whether they work on the new problems.

 And finally the standards by which the scientist judges the new solutions will be the standards that are embodied in the original exemplars.  So, although exemplars differ from rules in their content, they are similar to rules in their functions.  Exemplars are specific in content, but general in import and, according to Kuhn, they structure scientific research, guiding scientists in the selection of new problems, in the construction of possible solutions, and in the evaluation of the solutions proposed.

Normal Science Crisis Revolution

ScientistEngineer Wildly intelligent Unconventional Full of new ideas Earnest Hard-working Intellectually conservative

 The history of science is a graveyard of putative entities that turn out not to exist, of putative processes that turn out not to take place and of theories that turn out to be false.  Almost every scientific theory, more than - choose your own figure or 200 years old, we now know to be, strictly speaking, false.

 All past theories have been found to be false and therefore it is very likely that all present theories and, probably, all future theories, will eventually be found to be false as well.  Our best current theories may look terrific at the moment. If we step back a little and achieve some historical perspective, we should say that it is just a matter of time before the warts start to show. We will find out that we are wrong now, as we were in the past.

 Thornton, Stephen (2006). "Karl Popper". Stanford Encyclopedia of Philosophy. Retrieved "Karl Popper"  Popper, Karl The Logic of Scientific Discovery, London: Hutchinson,  Popper, Karl (2004 reprint). The logic of scientific discovery. London & New York: Routledge Classics. ISBN Popper, KarlThe logic of scientific discoveryISBN  Kuhn, Thomas The Structure of Scientific Revolutions, 2nd ed., Chicago: University of Chicago Press,  Kuhn, Thomas The Essential Tension, Chicago: University of Chicago Press,  Putnam, Hillary Meaning and the Moral Sciences, London: Hutchinson,  Lipton, Peter Inference to the Best Explanation 2nd edition, London: Routledge, 2004.

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